The present invention pertains to high dielectric constant films. More particularly, the present invention relates to methods and apparatus for forming high dielectric constant films utilizing the incorporation of atomic oxygen during the formation of such films.
Various dielectric films have been formed in the past during the fabrication of semiconductor devices. For example, films such as silicon dioxide and silicon nitride have been used for dielectric films in the formation of capacitors, such as for memory devices, including dynamic random access memories and static random access memories. Such films typically have small leakage currents associated therewith.
With the shrinkage of minimum feature sizes of semiconductor devices, the requirement of providing high capacitance with thinner films is becoming apparent. As the dielectric constant of silicon dioxide and silicon nitride are relatively low, the need for utilizing higher dielectric constant films, such as tantalum pentoxide (Ta2O5), strontium titanate oxide (SrTiO3), and barium strontium titanate (BaxSr1xe2x88x92xTiO3) arises. Such high dielectric films provide the ability to achieve a larger capacitance value in a smaller area, i.e., with a thinner dielectric film.
However, conventional deposition processes for forming such high dielectric constant films result in films having leakage current levels that are unacceptable for semiconductor devices being fabricated. As described in the article entitled, xe2x80x9cLeakage Current Mechanisms of Amorphous and Polycrystalline Ta2O5 Films Grown by Chemical Vapor Deposition,xe2x80x9d by Aoyama et al., J. Electrochem. Soc., Vol. 143, No. 3, March 1996, various treatments have been carried out after Ta2O5 film deposition to reduce the leakage current thereof. For example, such treatments described included dry O2 treatment, dry O3 treatment, O2 treatment with utilization of ultraviolet exposure, O3 treatment with use of ultraviolet exposure, and N2O plasma treatment. The results from the paper indicate that the presence of impurities, such as carbon and hydrogen, remaining in the Ta2O5 film leads to generally high leakage current and that oxidation of such impurities results in the reduction of the leakage current. However, post-deposition oxidation of such impurities results in a fabrication step generally not applicable to other dielectric films such as silicon dioxide and silicon nitride. Such post-deposition oxidation of high dielectric films, hereinafter referred to generally as post-deposition oxygen anneal, in addition to reducing throughput of devices also increases the thermal budget for fabrication of the devices.
Therefore, there is a need in the art for high dielectric oxide film formation methods and apparatus for forming high dielectric films, reducing throughput of devices by eliminating steps in the deposition process. The present invention provides such methods and apparatus for overcoming the problems as described above and other problems that will be readily apparent to one skilled in the art from the description of the present invention below.
A method of forming a high dielectric oxide film conventionally formed using a post-formation oxygen anneal to reduce the leakage current of such film is described. The method in accordance with the present invention includes forming a high dielectric oxide film on a surface. The high dielectric oxide film has a dielectric constant greater than about 4. The high dielectric oxide film includes a plurality of oxygen vacancies as the film is formed. The high dielectric oxide film is exposed to an amount of atomic oxygen during formation thereof sufficient for reducing the number of oxygen vacancies and eliminating the post-formation oxygen anneal of the formed high dielectric oxide film.
In one embodiment of the method, the amount of atomic oxygen to which the high dielectric oxide film is exposed during formation thereof is controlled as a function of the amount of oxygen incorporated into the high dielectric oxide film. In another embodiment of the method, the amount of atomic oxygen is controlled as a function of the concentration of atomic oxygen in a process chamber used for formation of the high dielectric oxide film.
In other embodiments of the method, the atomic oxygen is provided by at least one of O3, NO, and N2O. Further, the atomic oxygen may be provided by generation of a plasma from at least one of O3, NO, N2O, or O2. Ionized atomic oxygen generated by the plasma may be attracted to the surface for incorporation in the high dielectric oxide film by biasing the surface. Further, the plasma may be generated remotely of the surface upon which the high dielectric film is formed or in proximity to the surface.
In other embodiments of the method, the high dielectric film may include Ta2O5, BaxSr1xe2x88x92xTiO3, Y2O3, TiO2, HfO2, PZT, PLZT, or SBT. Further, the atomic oxygen utilized for exposing the high dielectric oxide film may be exposed to a heat source.
In another method of forming a dielectric film in the fabrication of semiconductor devices, an amount of atomic oxygen for use in the formation of the film on a surface is provided. The high dielectric oxide film has a dielectric constant greater than about 4. A vaporized precursor is also provided for use in the formation of the film. The high dielectric oxide film is then formed using the atomic oxygen and the vaporized precursor. The amount of atomic oxygen is controlled as a function of the amount of atomic oxygen necessary to reduce the leakage current levels to below a predetermined level.
In another method of forming a dielectric film in the fabrication of semiconductor devices, atomic oxygen is provided for use in the formation of a Ta2O5 film on a surface. A vaporized tantalum precursor is also provided for forming the film. The Ta2O5 film is formed using the atomic oxygen and the vaporized tantalum precursor while simultaneously performing an in situ oxygen anneal of the film. In one embodiment of this method, the precursor is a carbon-free solid precursor.
An apparatus for forming a high dielectric oxide film in accordance with the present invention is also described. The apparatus includes a controllable atomic oxygen source and a vaporized precursor source. A deposition chamber for receiving the atomic oxygen from the atomic oxygen source and vaporized precursor from the vaporized precursor source is utilized for locating a structure therein for deposition of the high dielectric oxide film on a surface thereof. The high dielectric oxide film has a dielectric constant greater than about 4. The apparatus further includes a detection mechanism for detecting a characteristic of the deposition of the high dielectric oxide film on the surface of the structure. The controllable atomic oxygen source is controlled as a function of the detected characteristic.
Further, in accordance with the present invention, a high dielectric oxide film is provided. The high dielectric oxide film includes one of Ta2O5, BaxSr1xe2x88x92xTiO3,Y2O3, TiO2, HfO2, PZT, PLZT, and SBT. The dielectric film is formed by depositing the high dielectric oxide film on a surface while exposing the high dielectric oxide film during formation thereof to a concentration of atomic oxygen sufficient for reducing oxygen vacancies therein and sufficient to eliminate a post-formation oxygen anneal of the high dielectric oxide film. In one embodiment of the high dielectric oxide film, the film is deposited on an electrode of a capacitor in a semiconductor memory device.